Breast pumps are well known devices for extracting milk from a breast of a user. A breast pump may be used if the baby or infant is not itself able to express milk from the breast, or if the mother is separated from the baby or infant, for example, if away from the baby at work. The use of a breast pump to express milk may also be used to stimulate and increase milk production in women with a low milk supply.
Breast pumps make use of a vacuum to induce milk expression from a nursing mother's breast. The pumping action of the device draws the milk from the nipple to a collection vessel, and the pressure and/or frequency may generally be adjusted to the preferences of the mother.
WO 2004/058330 discloses a manual breast pump comprising a breast cup, a pump housing with a piston and an activation mechanism in the form of a handle, together with a container for collection of the milk. The breast cup comprises a preferably rigid outer part and an inner, preferably completely or partially flexible, part, where two mutually separate chambers are provided between the outer part and the inner part. The piston comprises a membrane that connects the periphery of the piston with the wall of the pump housing and thereby divides the pump housing into an upper chamber and a lower chamber, wherein said upper chamber is in fluid contact with the chambers of the breast cup with the help of two openings with associated tubes, and the lower chamber is in fluid contact with the inside of the breast cup.
A general embodiment of a known breast pump for extracting milk from a user's breast is shown in FIG. 1. Such a breast pump 1 comprises a main body 2 and a collection vessel 3, such as a feeding bottle or bag. The collection vessel 3 is attached to the main body 2 by a screw fitting.
A breast-receiving funnel 5 extends from the main body 2 for receiving the breast of a user. The funnel 5 has an inner surface 6 and comprises a mouth 7 and a throat 8. The mouth 7 is open at an outer end and the inner surface 6 of the funnel 5 converges from the outer end towards the throat 8 to form a hollow recess in which a breast is received.
A vacuum pump unit 9 is fluidly connected to the main body 2 or is formed in the main body 2 to create a vacuum, and is generally operated by means of a user manually operating a handle 4 or by means of an electric motor actuating the vacuum pump.
However, a problem with the above described breast pump arrangement is that a negative pressure is generally generated at the breast to encourage milk expression by the pump unit producing a negative pressure below the atmospheric pressure. Therefore, it is known for milk to be drawn into the pumping mechanism. This can lead to unhygienic situations because pumping mechanisms are difficult or impossible to clean by a user.
It is also known to provide breast pumps with an insert which provides active massaging or kneading of the breast and/or nipple during milk extraction, to improve the rate of milk extraction and the comfort of the user. However, such an operation requires generation of a positive pressure in the insert and so a separate pump is required to generate such a pressure profile.